docs: def weighted(self):
          """
              This method creates a weighted copy of the internal formula. As a
              result, an object of class :class:`WCNF` is returned. Every clause
              of the CNF formula is *soft* in the new WCNF formula and its weight
              is equal to ``1``. The set of hard clauses of the formula is empty.
  
              :return: an object of class :class:`WCNF`.
  
              Example:
  
              .. code-block:: python
  
                  >>> from pysat.formula import CNF
                  >>> cnf = CNF(from_clauses=[[-1, 2], [3, 4]])
                  >>>
                  >>> wcnf = cnf.weighted()
                  >>> print wcnf.hard
                  []
                  >>> print wcnf.soft
                  [[-1, 2], [3, 4]]
                  >>> print wcnf.wght
                  [1, 1]
          """
  
          wcnf = WCNF()
  
          wcnf.nv = self.nv
          wcnf.hard = []
          wcnf.soft = copy.deepcopy(self.clauses)
          wcnf.wght = [1 for cl in wcnf.soft]
          self.topw = len(wcnf.wght) + 1
          wcnf.comments = self.comments[:]
  
          return wcnf